Electric valve circuit



, Jami 5, 1935.

A. S. FITZ GERALD ELECTRIC VALVE CIRCUIT Filed Jan. 10, 1931 u "KM fig; :ld

20 g a ,0 I A ,zz j 22 23 NWWL Inventor: Alan S. Fitzgerald;

H is Attofn ey.

Patented Jan. 15 1935 PATENT OFFICE ELECTRIC VALVE CIRCUIT Alan S. Fitz Gerald, Wynnewood, Pa., assignor to General Electric Company, a corporation of New York Application January 10, 1931, Serial No. 507,906

23 Claims.

My invention relates to electric valve circuits and more particularly to such circuits including valves of the thermionic cathode type.

In the operation or" electric valves of the thermionic cathode type, such for example as those having incandescent cathodes or those provided with electron emitting cathodes activated from an independent heater, it is essential to the satisfactory operation of the valves that the oathode shall have reached their normal operating temperature before the valves are energized to carry the load current of the translating ,circuit in which they are used and that the current in the valves should be interrupted in case their cathodes dropsubstantially below their normal operating temperatures. This is especially true in the case of electric valves of the vapor electric discharge type which rely primarily for their operation upon the ionization of the contained vapor. If a valve of this type is energized to carry the current of the translating circuit before its cathode reaches its proper temperature, a large part of the potential of the translating circuit will be consumed in the valve, the effect of which is to destroy the electronv emitting properties of the cathode by positive ion bombardment.

It is an object of my invention to provide an improved arrangement of apparatus and method of operating the same whereby an electric valve of the thermionic cathode type is prevented from operating in a translating circuit whenever the cathode of the valve is below its normal operating temperature. v

It is another object of my invention to provide an improved electric translating circuit including. an electric valve ,of the thermionic cathode type in which the normal flow of current in the valve will be delayed until its cathode reaches its proper operating temperature.

It is a further object of my invention to provide an improved electric translating circuit including an electric valve of the thermionic cathode type, provided with a heating circuit for the cathode, in which the current through the valve will beinterrupted in case the energization of the heating circuit drops below a predetermined value.

i It is a still further object of my invention to provide an improved electric translating circuit including an electric valve of the thermionic cathode type, provided with a cathode heating circuit, in which the operation of the valve in the circuit will be prevented unless its cathode is at a proper temperature and the energization of its heating circuit is above a predetermined value.

In accordance with the illustrated embodiment of my invention an electric valve is adapted to be connected in a translating circuit through a. two-position electric switch. This switch is normally biased to connect the anode of the electric valve to a source of relatively low potential, such for example as a low potential tap on the transformer winding which supplies the translating circuit. A second circuit including a uni-laterally conductive device is connected in parallel to the electric valve in' this position of the switch and these two parallel circuits includ'e' oppositely wound saturating windings of an. impedance device. The heating circuit for the cathode of the valve includes a. series transformer from the secondary winding of which is energized a relay which controls the actuating coil of the switch. When the cathode of the valve is cold its conductivity is very low with the result that the current flowing through the parallel circuit saturates the impedance device and thus reduces its impedance to a minimum. This impedance is connected directly across the primary winding of the series transformer and serves practically to short circuit it when saturated. However, when the temperature of the cathode rises to its proper value and the valve becomes fully conducting, the currents flowing in the two parallel circuits are substantially equal and the impedance device becomes unsaturated. Thus, in order for the electric valve to be connected in the translating circuit, it is necessary that the electric valve shall have attained substantially its normal conductivity and that substantially normal current is flowing in the cathode heating circuit.

For a better understanding of my invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims. The single figure of the accompanying drawing illustrates my invention as applied to an arrangement for interconnecting an alternating current supply circuit and a loadcircuit through an electric valve.

Referring more particularly to the drawing, I have illustrated a translating circuit for receiving energy from an alternating current circuit and delivering it to a load circuit 11. This translating circuit includes a transformer 12, the primary winding of which is connected to the supply circuit 10 and the secondary winding .tial of the load circuit 11.

of which is connected to the load circuit 11 through an electric valve 13 and a two-position switch 14. The secondary winding of the transformer 12 is provided with a low'potential tap 15, the potential of which is determined by the characteristics of electric valve 13, but is preferably low relative to the normal operating poten- Electric valve 13 may be of any of the several types well known in the art, although my circuit is particularly applicable to the use.of a valve of the vapor electric discharge type provided with a control grid. The switch 14 has two operative positions and is biased to the left-hand position, as shown in the drawing, by means of a spring'16 or other wellknown means. The switch 14 is adapted'to be moved to its right-hand position against the bias of the spring 16 by means of an operating solenoid 17 which is energized from an alternating current circuit 18 through the upper contacts of a relay 19. The alternating current circuit 18 may be connected directly to the supply circuit 10 if desired. Electric valve 13 is shown as being provided with a. cathode heater 20, though it will be obvious that, if desired, the cathode may. comprise the heated filament itself. The heater 20 is adapted to be energized from the secondary Winding of a transformer 21, the primary winding of which is connected across the alternating circuit 18 through the primary winding of a current transformer 22. In order to prevent the connection of electric valve 13 in the translating circuit before its cathode becomes heated to a proper temperature, the anode of the valve 13 is connected through a contact 23 of switch 14 and a variable resistor 25 to the low potential tap 15,

while the cathode of valve 131s connected to the lower terminal of the secondary winding of transformer 12 through a saturating winding 26 of a reactor 28 provided with alternating current or impedance windings 29 and,30. The contact 24 of the switch 14 also completes a second circuit across the low potential winding of the transformer which includes variable resistor 25, contacts 23 and 24 of switch 14, a variable resistor 31', a unilaterally conductive device, such for example, as a contact rectifier 32, and a second saturating winding 27 of the reactor 28. The saturating windings 26 and 27 are differentially wound so that when the currents through them are equal the reactor 28 is unsaturated. The impedance windings 29 and 30 of reactor 28 are connected in parallel to the primary winding of the currenttransformer 22 through the lower contacts of relay 19. The operating coil of relay 19 is connected to the secondary winding of current transformer-22 through a pair of unilaterally conductive devices 33 and 34, such, for example, as contact rectifiers. The devices 33 and 34, together with the secondary winding of the transformer 22, comprise in efiect a full wave rectifier, the direct current side of which is con nected across the operating coil of relay 19. If desired, a condenser 35 may beconnected in parallel to the relay coil to smooth out the ripples of thedirect current. It will be obvious to those skilled in the art thatin case the relay coil of the relay 19 is designed to operate from alternating current the. devices 33 and 34 andv the condenser 35 may be omitted.

In order to prevent the breaking of the current flowing in the translating circuit or in the low potential circuit at the contacts 23 or 36 when the switch 14 is operated from one position to the other, I have provided a grid circuit for valve 13 which is controlled by auxiliary contacts associated with switch 14 and acts to impress a negative potential upon the grid during the interval of switch operation. This arrange-.

connected through contacts 41 to a circuit 42 which may include any means for controlling the potential of the grid in any desired manner according to the system in which the valve is included. In referring to certain of the auxiliary contacts of the switch member 14 as being normally closed and others as normally opened, it is intended to describe the position of these auxiliary contacts whenthe switch member 14 is in its normal biased position. The switch meme ber 14 is provided with spring actuated wiping contacts 43 to insure'that the contacts 37 are broken and that the-contacts 40 are closed before the circuit is interrupted at the contact 23 when the switch is moving to its right-hand posi-' tion and to insure that the contacts 41 are open and the contacts 40 closed before the circuit is broken at the contact 36,-when moving to its left-hand position.

In explaining the operation of the above-described apparatus, it-will be assumed that the supply circuit 10 is initially energized, that the circuit 18 is subsequently energized and that the several moving parts are in the position shown in the drawing. Under these conditions, a low potential is impressed between the-anode and cathode of electric valve 13' from the low potential tap 15 through resistor 25, contact 23 of switch 14, valve 13 and saturating winding 26 of reactor 28. However, due to the fact that the circuit 18 is energized subsequently and to the fact that an appreciable interval of time is required to heat the cathode of the valve 13 to a proper temperature, no current will initially flow in this circuit. Even when current does begin to flow, the deleterious effect of positive ion bombardment on the cathode will not be produced at this reduced anode potential. At the same time a parallel circuit is completed from the low potential tap 15 through resistor 25, contacts 23 and 24 of switch 14, resistor 31, rectifier device 32 andthe saturating winding 27 of reactor 28. A current will flow in this circuit comes energized, the current drawn by the cathode heater 20 through thetransformer 21 and current transformer 22, tends to induce a suflicient potential in secondary winding of thetransformer 22 to pick up the relay 19. However, the impedance windings of reactor 28 are connected in parallel to the'primary winding of this transformer through the lower contacts of relay 19 and, since this reactor is completely saturated, its impedance is substantially zero so that the current transformer is practically short circuited. As energy is supplied to the cathode heater 20, the cathode temperature gradually rises, slowly increasing the conductivity of valve 13 and allowing a current to flow through the described above, the rate at which this current rises depending of course upon the characteristics of the valve 13. The values of the resistors 25 and 31 are so chosen that when the cathode of the valve 13 reaches its normal operating temperature, the currents flowing in the saturating windings 26 and 27 will be exactly equal, their saturating effect will neutralize each other, and the impedance of windings 29 and 30 will be a maximum. Current will now flow through the primary winding of current transformer 22 and when the cathode of electric valve 13 reaches its proper temperature and the current flowing in the heating circuit is above a predetermined value, the relay 19 will become energized to close its upper contact through which the operating coil 17 of the switch 14 is energized. Switch 14 is now moved to its right-hand position connecting the anode of electric valve 13 to contact 36 thus completing the connections of the translating circuit.

If the cathode heater 20 should become burned out, or in case the heater current should'be interrupted for any cause, it is desirable that the valve 13 should be disconnected from the transis maintained at a proper temperature and the current flowing in the heating circuit is above a predetermined value.

It will be noticed that, when the switch 14 is in its normal position, the grid of valve 13 is energized from a positive bias battery 38 through the contacts 37 in order to insure that the conductivity of thevalve is limited only by its cathode temperature. As soon as switch 14 begins to move under the influence of the operating solenoid 1'7, the contacts 37 are opened and the contacts 39 are closed. In order that this opening and "closing of the contacts may be completed before the switch member breaks the contact 23, the switch member is provided with wiping contacts 43. to maintain engagement with the respective contacts 23 and 36 during the initial portion of the operation of the switch in either direction. When the wiping contacts 43 are disengaged from both contacts 23 and 36, that is, when the switch is in its neutral position, contacts 39 and 40 are closed and the grid of valve 15 is connected .to a negative bias battery 44. With this arrangement the grid of electric valve 13 is made negative before the circuits are broken at either contacts 23 or 36 so that current is interrupted in the valve at the end of the half cycle of alternating anode potential. This arrangement insures that the current will always be broken in the valve 13 rather than at the contacts'23 or 36 when the switch is operated from one position to the other. When the switch member 14 is operated to its final position to connect the valve 15 in the translating circuit, the auxiliary contacts 40 are opened and the contacts 41 are closed to connect the grid of the valve 13 to the circuit 42 by means of which the current flowing through the valve may be controlled in any well-known manner.

While this last-described grid-potential controlcircuit is particularly suitable for use in connection with the general system described above, it is to be clearly understood that it is of general application and may be used wherever it is desired to switch an electric valve in and out of a power circuit.

While I have described what I at present consider the preferred embodiment of my invention, it will be obvious tothose skilled in the art that various changes and modifications may be made without departing from my invention and I, therefore, aim in the appended claims to cover all such changesv and modifications as tall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is,

1. In combination, an electric translating circuit, an electric valve provided with an anode and a thermionic cathode, means for connecting the anode-cathode circuit of said'valve in said translating circuit, and means responsive to the conductivity of said valve for controlling the operation oi? said connecting means.

2. In combination, an electric translating circuit, including a source of potential, an electric valve provided with an anode and a thermionic cathode, means for connecting the anode-cathode circuit of said valve in said translating circuit, means for impressing between said anode and cathode a potential substantially less than that of said source, and means responsive to the current through said valve for controlling said connecting means.

3. In combination, an electric translating circuit including a source of potential, an electric valve provided with an anode and a thermionic cathode, means for connecting the anode-cathode circuit of said valve in said translating circuit, a second source of potential substantially less than that of said first source, an electrical difierential device, a pair of parallel circuits connected across said second source, one of said circuits including the anode-cathode circuit of said valve and each of said circuits including an element of said differential device, and means controlled by said differential device for controlling said connecting means.

4. In combination, an alternating current circuit provided with a point of intermediate potential, an electric valve provided with an anode and a thermionic cathode, means for connecting the anode-cathode circuit of said valve in said alternating current circuit, an impedance device provided with a pair of difierentially wound saturating windings, a pair of parallel circuits connected from one side of said alternating current circuit to said point of intermediate potential, one of said circuits including the anodecathode circuit of said valve, the other including a unilaterally conductive device, and each including one of said saturating windings, and means responsive to the saturation of said impedance device for controlling said connecting means.

5. In combination, an alternating current circuit provided with a point of intermediate potential, an electric valve provided with an anode and a thermionic cathode, an impedance device provided with a pair of differentially wound saturating windings, a pair of parallel circuits, one including, the anode-cathode circuit of said valve, the other including a unilaterally conductive device and each being connected to one side of said alternating current circuit through one of said saturating windings, a two position elecbiased to open position, -a heating circuit for said cathode including a series transformer, and means energized from said transformer to overcome said bias and operate said switch when the current in said heating circuit rises to a predetermined value.

7. In combination, an alternating current cir-. cuit provided with a point of intermediate po tential, an electric valve providedwith an anode and a thermionic cathode, an impedance device having a'pair of difierentially wound saturating windings, a pair of parallel circuits, one including the anode-cathode circuit of said valve, the other including a unilaterally conductive device and each being connected to one side of said alternating current circuit through one of said saturating windings, a two-position electric switch adapted to connect said parallel circuits to said point of intermediate potential and to connect the anode-cathode circuit of said valve directly in said alternating current circuit, respectively, said switch being biased to said first position, a heating circuit for said cathode including a series transformer having primary and secondary windings, said impedance device'being connected in parallel to said primary winding, and means energized from said secondary winding for operating said switch.

'8. In combination, an alternating current circuit, an electric'valve, circuit controlling means for connecting said valve in said circuit and disconnecting it therefrom, and means for rendering said valve conductive for a final portion of the cycle of operation of said circuit controlling means less than that during which the circuit is completed through said circuit controlling means.

9. In combination, an alternating current translating circuit, an electric valve for controlling said circuit, a second circuit controlling means for connecting said valve in said circuit and disconnecting it therefrom, and means for preventing the interruption or initiation of the current in t he translating circuit by said second circuit controlling means.

10. In combination, an alternating current translating circuit, an electric valve normally connected in said circuit for controlling the same, means for disconnecting said valve from said circuit, and means for insuring /that the current flowing in 'said circuit will be interrupted in said valve "upon operation of said means to disconnect said valve from said circuit.

11. In combination, an alternating current translating circuit, an electric valve provided with acontrol grid, means for connecting said valve in said translating circuit, and means for impressing a negative potential on said control grid during the operation of said connecting means.

12. In combination, two alternating current circuits, an electric valve, means for transferring trol grid, a transfer switch for serially connecting said valve in either circuit, an auxiliary contact associated with said switch, and a grid circuit for said valve including said auxiliary contact whereby a negative potential is impressed upon said grid when either of said alternating current circuits is broken through said switch.

15. In combination, an electric translating circuit including a source of potential, 'an electric valve provided with an anode, a thermionic cathode and a control grid, means for connecting the anode-cathode circuit of said valve in said translating circuit, means for impressing between said anode and cathode a potential substantially less than that of said source, means for simultaneously impressingapositive potential upon said control grid, and means responsive to the current through said valve for controlling said connecting means. v

16. In combination, an electric translating circuit including a source of potential, an electric valveprovided with an anode, a thermionic cathode and a control grid, means for connecting the anode-cathode circuit of said valve in said translating circuit, means for impressing between said anode and cathode a potential substantially less than that of said source, auxiliary contacts associated with said connecting means for'simultaneously impressing a positive potential upon said control means, a grid control circuit, other contacts associated with said connecting means for connecting said grid to said control circuit, means responsive to the current through said valve for controlling said connecting means, and means actuated by the operation of saidconnecting means for opening said auxiliary contacts and closing'saidother contacts. v

17. In combination, an electric translating circuit including a source of potential, an electric valve provided with an anode, a thermionic cathode, and a control grid, a heating circuit for said cathode, a two position switch for connecting the anode-cathode circuit of said valve in said translating circuit but biased to connect said anode to a circuit including means for impressing between said anode and cathode a po-' tential substantially less than that of said source, acircuit including contacts associated with said switch for simultaneously impressing a positive potential upon said control grid, means responsive jointly to the current through said valve and the energization of said heating circuit for operating said switch against its bias, 2. control circuit for said grid, other contacts associated with said switch to connect said grid to said control circuit, and means operated by said switch for opening said first-mentioned contacits and closing said second-mentioned contac s. l l

18. In combination, an alterating current circuit, an electric valve provided with an anode, a 4

thermionic cathode, and a control grid, a heating circuit for said cathode, a two-positionswitch for connecting the anode-cathode circuit of said valve in said alternating current circuit but biased to connect said anode to a circuit including means for impressing between said anode and cathode a potential substantially less than that of said alternating current circuit, a circuit including a set of normally closed contacts associated with said switch for simultaneously impressing a positive potential upon said control, means responsive jointly to the current through said valve and the energization of said heating circuit for operating said switch to its other position, a circuit including a second set of contacts associated with said switch for impressing a negative potential upon said control grid while said switch is intermediate its two operative positions, a control circuit for said grid, a third set a of contacts associated with said switch to contemperature, and connecting said valve directly in said translating circuit. a

20. The method of connecting into a translating circuit an electric valve provided with an anode and a thermionic cathode which comprises connecting a source of reduced potential between said anode and cathode, disconnecting said source when said valve reaches a predetermined degree of conductivity, and connecting said valve directly in said translating circuit.

21. The method of connecting .into a translating circuit an electric valve provided with an anode and a thermionic cathode which comprises connecting a source of reduced potential between said anode and cathode, disconnecting said source potential when the current through said valve rises to a predetermined value, and connecting said valve directly in said translating circuit.

22. The method of connecting into a translating circuit an electric valve provided with an anode, a thermionic cathode, and a control grid, which comprises connecting a source of reduced potential between said anode and cathodp, simultaneously impressing a positive potentiat on said controlgrid, disconnecting said source and said grid potential when said cathode reaches a predetermined temperature, and connecting said valve directly in said translating circuit.

23. The method of connecting into a translating circuit an electric valve provided with an anode, a thermionic cathode, and a control grid, which comprises connecting a source of reduced potential between said anode and cathode, simultaneously impressing a positive potential on said control grid, disconnecting said source and said grid potential when said cathode reaches a predetermined temperature, connecting said valve directly in said translating circuit and simultaneously connecting'said grid to a control circuit, and connecting said control grid to a source of negative potential during the interval when; the connections to said valve are being changed.-

ALAN S. FITZ GERALD. 

